Newbie question : Power Subwoofer, Yes; But what does the receiver do then

[supo]

If I have a powered sub, why do I need a receiver? Can I not connect the speakers directly to the cd player since the sub is powered?
Can somebody sinnplify this please !
Apart from radio and switching between various sources, what other function does a receiver perform ? Has it got an amplifier inside?

 

[Flimber]

1. To switch sources, to decode surround formats, to have remote-controllability (esp. volume).

2. A subwoofer usually powers itself (i.e., it's own internal mono amplifier is for it's own woofer) and is called an Active Subwoofer. Some allow connection of sources directly, even your other speakers, but they are AV in-a-box systems with decoding built into the sub. You could use the latter type of sub with an AV switching unit to expand the number of inputs (i.e., you wouldn't need a reciever). However, a seperate reciever, speakers and an Active Sub would be preferable.

3. Yes, several. For your other speakers.

HTH,
Mike.

 

[supo]

Thanks for a quick reply ,and its getting clearer!

 

[Reiner]

If I have a powered sub, why do I need a receiver?

In stereo systems you will often find passive subs since most stereo amps don't have a subwoofer out / bassmanagement while it's common for AV systems to use an active (aka powered) sub.

A powered sub is needed to free the amplifier/receiver of the load. To drive a non-powered sub (aka a passive sub) you need some meaty amplification - and most amps/receivers can't cope with that as they have to deal with at least 5 channels. Often budget amps/receivers have to compromise somewhere and cutting cost at the power supply section is often part of it (also reduces the size).

Can I not connect the speakers directly to the cd player since the sub is powered?

The sub has actually nothing to do with that. Speakers cannot be connected directly to a CDP (or other sources) as you need some kind of amplification and volume control, like an AV amplifier or an AV receiver.
Remember that a powered sub is also connected to the amp/receiver - but using line level (non-amplified) signal only - as you need to control the sub's volume with the rest of the system.

Apart from radio and switching between various sources, what other function does a receiver perform ? Has it got an amplifier inside?

AV amplifiers and receivers perform the following functions:

• Pre-amplification / volume control
  Decoding of various sound formats & DSP (Digital Signal Processing) like bassmanagement for example
  Video and Audio switching of sources
  OSD (On-screen Display)
  Power amplification (typically 5-7 channels)

Some flagship amps have more channels, either for another Zone or for proprietary processing, e.g. Yamaha front effects that require additional channels and speakers.
Newer amps also do video conversion and/or scaling of video sources.